He has to be able to control the battle really well if he wants to get anything done at all and survive. Youpi is a monster, after all. But that's why I listed earlier the two details that look really promising for Killua at the moment. The third is the fact Killua is a lot faster, but that goes without saying. Youpi couldn't catch even Knuckle.
I talk previews when the episode itself doesn't really have anything worth discussing or the preview looks super promising. It's not really such an issue with HxH most of the time, seeing how it follows the manga and isn't stretching it all the way to hell and back.